Lithium batteries utilizing nanoporous separator layers

ABSTRACT

Provided are methods of preparing lithium batteries comprising a separator/electrode assembly having one or more current collector layers interposed between first and second electrode layers of the same polarity, wherein the first electrode layer is coated or laminated overlying a separator layer and the separator/electrode assembly is interleaved with an electrode comprising a current collector layer interposed between two electrode layers of opposite polarity to said first and second electrodes.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/302,748, filed Nov. 22, 2011, titled Lithium BatteriesUtilizing Nanoporous Separator Layers that is a continuation-in-part ofPCT Application No. PCT/US2010/001536, filed May 26, 2010, which claimsthe benefit under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication No. 61/217,132, filed May 26, 2009. The present applicationis a continuation of U.S. patent application Ser. No. 13/302,748, filedNov. 22, 2011, titled Lithium Batteries Utilizing Nanoporous SeparatorLayers that is also a continuation-in-part of PCT Application No.PCT/US2010/001537, filed May 26, 2010, which claims the benefit under 35U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/217,132,filed May 26, 2009. The present application is a continuation of U.S.patent application Ser. No. 13/302,748, filed Nov. 22, 2011, titledLithium Batteries Utilizing Nanoporous Separator Layers that is also acontinuation-in-part of PCT Application No. PCT/US2010/001539, filed May26, 2010, which claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 61/217,132, filed May 26, 2009. Thepresent application is a continuation of U.S. patent application Ser.No. 13/302,748, filed Nov. 22, 2011, titled Lithium Batteries UtilizingNanoporous Separator Layers that is also a continuation-in-part of PCTApplication No. PCT/US2010/001535, filed May 26, 2010, which claims thebenefit under 35 U.S.C. §119(e) of U.S. Provisional Patent ApplicationNo. 61/217,132, filed May 26, 2009.

The entireties of each of the above-referenced patent applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of batteries andother electric current producing cells. More particularly, thisinvention pertains to lithium batteries that utilize nanoporousseparators and to methods of preparing lithium batteries by takingadvantage of the nanoporous structure of the separator to overlay theother layers of the battery in a desired configuration.

BACKGROUND OF THE INVENTION

Lithium batteries, including rechargeable or secondary lithium ionbatteries, non-rechargeable or primary lithium batteries, and othertypes such as lithium-sulfur batteries, are typically made byinterleaving a plastic separator, a metal substrate with a cathode layercoated on both sides, another plastic separator, and another metalsubstrate with an anode layer coated on both sides. To maintain thealignment of the strips of these materials and for other qualityreasons, this interleaving is usually done on automatic equipment, whichis complex and expensive. Also, in order to achieve sufficientmechanical strength and integrity, the separators and the metalsubstrates are relatively thick, such as 10 microns in thickness ormore. For example, a typical thickness of the copper metal substrate forthe anode coating layers is 10 microns, a typical thickness of thealuminum metal substrate for the cathode coating layers is 12 microns,and the plastic separators typically have thicknesses ranging from 12 to20 microns. These thick separators and metal substrates are notelectrochemically active and thus lower the volume of the electroactivematerial in the electrodes that of the lithium batteries. This limitsthe energy density and power density of the lithium batteries.

Among the new applications for lithium batteries are high powerbatteries for hybrid, plug-in hybrid, and electric vehicles. In contrastto the cylindrical metal cells used in lithium batteries for portablecomputers and other applications, many of the lithium batteries forvehicles are of a flat or prismatic design. Also, the lithium batteriesfor vehicles need to be economical. Potential approaches to make higherenergy and more economical lithium batteries for vehicles and otherapplications include greatly increasing the proportion or percentage ofthe volume of the electroactive material in each battery and reducingthe complexity and expense of the automated equipment to fabricate thebattery.

It would be advantageous if a lithium battery comprised separator andmetal substrate layers that were much thinner than are currently usedand thereby had a greater content of electroactive material. It would beparticularly advantageous if this lithium battery could be fabricated onless complex and less expensive automated processing equipment than, forexample, the winding equipment utilized for portable computer batteries,and furthermore was particularly adapted for making flat or prismaticbatteries.

SUMMARY OF THE INVENTION

This invention pertains to batteries and other electric currentproducing cells, especially lithium batteries, that utilize nanoporousseparators, particularly heat resistant separators with dimensionalstability at temperatures at and above 200° C., and to methods ofpreparing lithium batteries by taking advantage of the nanoporousstructure of the separator to coat the other layers of the battery in adesired thickness and configuration on the separator.

One aspect of the present invention pertains to a lithium batterycomprising (a) a separator/electrode assembly, wherein the assemblycomprises a current collector layer interposed between a first electrodelayer and a second electrode layer of the same polarity and a porousseparator layer on the side of each of the two electrode layers on theside opposite to the current collector layer, and wherein each of theelectrode layers is coated directly on one of the separator layers, (b)an electrode, wherein the electrode comprises a current collector layerinterposed between two electrode layers of the opposite polarity to thefirst and second electrode layers of the same polarity, and (c) anelectrolyte, wherein the battery comprises alternating layers of theseparator/electrode assembly and the electrode. In one embodiment, aportion of the assembly is not in contact with the electrode.

In one embodiment of the lithium batteries of this invention, theportion of the assembly that is not in contact with the electrode is incontact with an additional one or more portions of the assembly that arenot in contact with the electrode. In one embodiment, a device havingelectrically conductive pins is in electrical contact with the portionof the assembly and the additional one or more portions of the assemblyand is not in electrical contact with any portion of the electrode.

In one embodiment of the lithium batteries of the present invention, aportion of the electrode is not in contact with the assembly. In oneembodiment, the portion of the electrode is in contact with anadditional one or more portions of the electrode that are not in contactwith the assembly. In one embodiment, a device having electricallyconductive pins is in electrical contact with the portion of theelectrode and the additional one or more portions of the electrode andis not in electrical contact with any portion of the assembly. In oneembodiment of the lithium batteries of this invention, a portion of theassembly is not in contact with the electrode and is in contact with anadditional one or more portions of the assembly that are not in contactwith the electrode. In one embodiment, a device having electricallyconductive pins is in electrical contact with the portion of theassembly and the additional one or more portions of the assembly and isnot in electrical contact with any portion of the electrode.

In one embodiment of the lithium batteries of this invention, the firstand second electrode layers of the assembly are cathode layers. In oneembodiment, the current collector layer of the assembly comprises analuminum layer. In one embodiment, the thickness of the aluminum layeris less than 3 microns.

In one embodiment of the lithium batteries of the present invention, thefirst and second electrode layers of the assembly are anode layers. Inone embodiment, the current collector layer of the assembly comprises ametal layer selected from the group consisting of a copper layer and anickel layer. In one embodiment, the thickness of the metal layer isless than 3 microns.

In one embodiment of the lithium batteries of this invention, the porousseparator layer comprises pores having an average pore diameter of lessthan 0.2 microns, and preferably less than 0.1 microns. In oneembodiment, the separator layer has a thickness of less than 9 microns,and preferably less than 6 microns. In one embodiment, the separatorlayer comprises a porous layer comprising aluminum boehmite.

Another aspect of the present invention pertains to methods of making alithium battery comprising the steps of (a) coating a porous separatorlayer on a substrate; (b) coating an electrode layer of one polaritydirectly on the separator layer; (c) coating one or more currentcollector layers directly on the electrode layer to make aseparator/electrode stack; (d) laminating two of the separator/electrodestacks together and delaminating the substrate from the separator layerto form a separator/electrode assembly having the one or more currentcollector layers interposed between the two electrode layers of theassembly; and (e) interleaving the assembly with an electrode comprisinga current collector layer interposed between two electrode layers ofopposite polarity to the electrode layer of step (b) to form a dryseparator/electrode cell. In one embodiment, the assembly and theelectrode are in a sheet configuration prior to the interleaving step.In one embodiment, after step (e), a portion of the assembly is not incontact with the electrode and a portion of the electrode is not incontact with the assembly, and wherein a first device with electricallyconductive pins electrically connects two or more of the portions of theassembly and a second device with electrically conductive pinselectrically connects two or more of the portions of the electrode. Inone embodiment, there are further steps of (1) enclosing the dryseparator/electrode cell in a casing and (2) filling with electrolyteand sealing.

In one embodiment of the methods of making lithium batteries of thisinvention, at least one of the one or more current collector layers ofstep (c) comprises a metal layer and the thickness of the metal layer isless than 3 microns. In one embodiment, the porous separator layercomprises pores having an average pore diameter of less than 0.2microns, and preferably less than 0.1 microns. In one embodiment, theseparator layer has a thickness of less than 9 microns, and preferablyless than 6 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, particular arrangementsand methodologies are shown in the drawings. It should be understood,however, that the invention is not limited to the precise arrangementsshown or to the methodologies of the detailed description.

FIG. 1 shows a cross-section view of the alternating layers of aseparator/electrode assembly and an electrode where a portion of theassembly is not in contact with the electrode.

FIG. 2 shows a cross-section view of a separator/electrode assembly witha current collector layer interposed between electrode layers andseparator layers.

FIG. 3 shows a cross-section view of an electrode with a currentcollector layer interposed between electrode layers.

FIG. 4 shows a cross-section view of a device with electricallyconductive pins that makes electrical connections between a portion ofthe assembly without making electrical connection with the electrode.

FIG. 5 shows a cross-section view of the alternating layers of aseparator/electrode assembly and an electrode where a portion of theelectrode is not in contact with the assembly.

FIG. 6 shows a cross-section view of a device with electricallyconductive pins that makes electrical connections between a portion ofthe electrode without making electrical connection with the assembly.

FIG. 7 shows a top-down view of the alternating layers where the device,as shown in FIG. 4, is in electrical contact with the portion of theassembly, as shown in FIG. 1, and with an additional one or moreunderlying portions of the assembly, and where the device, as shown inFIG. 6, is in electrical contact with the portion of the electrode, asshown in FIG. 5, and with an additional one or more underlying portionsof the electrode.

FIG. 8 shows a cross-section view of a separator/electrode stack afterthe steps to make the separator/electrode stack.

FIG. 9 shows the multilayer structure formed by laminating two of theseparator/electrode stacks together and prior to delaminating asubstrate.

DETAILED DESCRIPTION OF THE INVENTION

The lithium batteries and methods of preparing lithium batteries of thepresent invention provide a flexible and effective approach to lithiumbatteries with higher energy and power densities and with lowermanufacturing and capital equipment costs.

One aspect of the present invention pertains to a lithium batterycomprising (a) a separator/electrode assembly, wherein the assemblycomprises a current collector layer interposed between a first electrodelayer and a second electrode layer of the same polarity and a porousseparator layer on the side of each of the first and second electrodelayers opposite to the current collector layer, and wherein each of theelectrode layers is coated directly on one of the separator layers, (b)an electrode, wherein the electrode comprises a current collector layerinterposed between two electrode layers of the opposite polarity to thefirst and second electrode layers of the same polarity, and (c) anelectrolyte, wherein the battery comprises alternating layers of theassembly and the electrode. In one embodiment, a portion of the assemblyis not in contact with the electrode.

As used herein, the word “battery” pertains to both a single electriccurrent producing cell and to multiple electric current producing cellscombined in a casing or pack. As used herein, the term “lithium battery”refers to all types of lithium batteries known in the art, including,but not limited to, rechargeable or secondary lithium ion batteries,non-rechargeable or primary lithium batteries, and other types such aslithium-sulfur batteries.

As used herein, the term “current collector layer” refers to one or morecurrent collection layers that are adjacent to an electrode layer. Thisincludes, but is not limited to, a single conductive metal layer orsubstrate and a single conductive metal layer or substrate with anoverlying conductive coating, such as a carbon black-based polymercoating. Examples of a conductive metal substrate as the currentcollector are a metal substrate comprising aluminum, which is typicallyused as the current collector and substrate for the positive electrodeor cathode layer, and a metal substrate comprising copper, which istypically used as the current collector and substrate for the negativeelectrode or anode layer. The current collector layers of both theseparator/cathode assembly and the separator/anode assembly types of aseparator/electrode assembly may comprise an electrically conductivematerial selected from the group consisting of electrically conductivemetals including metal pigments or particles, electrically conductivecarbons including carbon black and graphite pigments, and electricallyconductive polymers. These electrically conductive materials may becombined with an organic polymer for added mechanical strength andflexibility to form the current collector layer.

As used herein, the term “electrode layer” refers to a layer of the cellthat comprises electroactive material. When the electrode layer is wherethe lithium is present in the case of primary lithium batteries or, inthe case of rechargeable lithium batteries, is formed during thecharging of the battery and is oxidized to lithium ions during thedischarging of the battery, the electrode layer is called the anode ornegative electrode. The other electrode of opposite polarity is calledthe cathode or positive electrode. Any of the electroactive materialsthat are useful in lithium batteries may be utilized in the electrodelayers of this invention. Examples include, but are not limited to,lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate,and sulfur as electroactive materials in the cathode layers and lithiumtitanate, lithium-intercalated carbon, lithium-intercalated graphite,and lithium metal as electroactive materials in the anode layers.

As used herein, the word “electrolyte” refers to any of the electrolytesthat are useful in lithium batteries. Suitable electrolytes include, butare not limited to, liquid electrolytes, gel polymer electrolytes, andsolid polymer electrolytes. Suitable liquid electrolytes include, butare not limited to, LiPF₆ solutions in a mixture of organic solvents,such as, for example, a mixture of ethylene carbonate, propylenecarbonate, and ethyl methyl carbonate.

FIG. 1 shows an example of a cross-section view (not to scale) of thealternating layers of a separator/electrode assembly 10 and an electrode20 where a portion 12 of the assembly 10 is not in contact with theelectrode 20. One purpose for having a portion of theseparator/electrode assembly that is not in contact with the electrode,such as, for example, the portion of the assembly having no overlying orunderlying layers of the electrode is to provide for an area of theseparator/electrode assembly where the individual current collectorlayers may be directly electrically connected to each other for moreefficient operation of the lithium battery. FIG. 2 shows an example of across-section view (not to scale) of a separator/electrode assembly 10of this invention with a current collector layer 14 interposed betweenelectrode layers 16 and separator layers 18. FIG. 3 shows an example ofa cross-section view (not to scale) of an electrode 20 of the presentinvention with a current collector layer 24 interposed between electrodelayers 26.

In one embodiment of the lithium batteries of this invention, theportion of the assembly that is not in contact with the electrode is incontact with an additional one or more portions of the assembly that arenot in contact with the electrode. In one embodiment, a device havingelectrically conductive pins is in electrical contact with the portionof the assembly and the additional one or more portions of the assemblyand is not in electrical contact with the electrode.

FIG. 4 shows an example of a cross-section view (not to scale) of adevice 30 with electrically conductive pins 32 that makes electricalconnections between two or more portions 12 of the assembly 10 withoutmaking electrical connection with the electrode 20.

In one embodiment of the lithium batteries of the present invention, aportion of the electrode is not in contact with the assembly. FIG. 5shows an example of a cross-section view (not to scale) of thealternating layers of a separator/electrode assembly 10 and an electrode20 where a portion 22 of the electrode 20 is not in contact with theassembly 10. Similarly to that described above for theseparator/electrode assembly, one purpose for having a portion of theelectrode that is not in contact with the separator/electrode assembly,such as, for example, the portion of the electrode having no overlyingor underlying layers of the assembly is to provide for an area of theelectrode where the individual current collector layers may be directlyelectrically connected to each other for more efficient operation of thelithium battery. In one embodiment, the portion of the electrode that isnot in contact with the assembly is in contact with an additional one ormore portions of the electrode that are not in contact with theassembly. In one embodiment, a device having electrically conductivepins is in electrical contact with the portion of the electrode and theadditional one or more portions of the electrode and is not inelectrical contact with the assembly. By the word “pins,” as usedherein, is meant any shape, such as, for example, rods, clamps with orwithout sharp protrusions that can penetrate multiple layers, and screwswith or without positioning holes in the casing or another part of theouter packaging to position the screws and hold them in place, that iseffective in electrically contacting all of the protruding layers orportions of either the separator/electrode assembly or the electrode.

FIG. 6 shows an example of a cross-section view (not to scale) of adevice 40 with electrically conductive pins 42 that makes electricalconnections between a portion 22 of the electrode 20 without makingelectrical connection with the assembly 10. In one embodiment, a portionof the assembly is not in contact with the electrode and is in contactwith an additional one or more portions of the assembly that are not incontact with the electrode. In one embodiment, a device havingelectrically conductive pins is in electrical contact with the portionof the assembly and the additional one or more portions of the assemblyand is not in electrical contact with any portion of the electrode. FIG.7 shows an example of a top-down view (not to scale) of the alternatinglayers where device 30, as shown in FIG. 4, is in electrical contactwith the portion 12 of the assembly 10, as shown in FIG. 1, and with anadditional one or more underlying portions 12 of the assembly 10, andwhere device 40, as shown in FIG. 6, is in electrical contact with theportion 22 of the electrode 20, as shown in FIG. 5, and with anadditional one or more underlying portions 22 of the electrode 20.

In one embodiment of the lithium batteries of this invention, the twoelectrode layers of the separator/electrode assembly are cathode layers.In one embodiment, the current collector layer of the assembly comprisesan aluminum layer. In one embodiment, the thickness of the aluminumlayer is less than 3 microns.

In one embodiment of the lithium batteries of the present invention, thetwo electrode layers of the separator/electrode assembly are anodelayers. In one embodiment, the current collector layer of the assemblycomprises a metal layer selected from the group consisting of a copperlayer and a nickel layer. In one embodiment, the thickness of the metallayer is less than 3 microns.

In one embodiment of the lithium batteries of this invention, the porousseparator layer comprises pores having an average pore diameter of lessthan 0.2 microns, and preferably less than 0.1 microns. In oneembodiment, the separator layer has a thickness of less than 9 microns,and preferably less than 6 microns. In one embodiment, the separatorlayer comprises a porous layer comprising a xerogel layer or xerogelmembrane, including, but not limited to, a porous layer comprisingaluminum boehmite.

By the term “xerogel layer”, as used herein, is meant a porous layerthat was formed by a xerogel or sol gel process of drying a colloidalsol liquid to form a solid gel material. By the term “xerogel membrane”,as used herein, is meant a membrane that comprises at least one layercomprising a xerogel layer where the pores of the xerogel layer arecontinuous from one side of the layer to the other side of the layer.Xerogel layers and membranes typically comprise inorganic oxidematerials, such as aluminum oxides, aluminum boehmites, and zirconiumoxides, as the sol gel materials. Examples of suitable xerogel membranesfor the present invention include, but are not limited to, the xerogelmembranes described in U.S. Pat. Nos. 6,153,337 and 6,306,545 to Carlsonet al. and U.S. Pat. Nos. 6,488,721 and 6,497,780 to Carlson.

Many inorganic oxide materials, such as, for example, aluminum oxidesand aluminum boehmites, are non-flammable and do not melt attemperatures below 1000° C. Porous separator layer that comprise theseinorganic oxide materials in a xerogel membrane or as a blend ofinorganic oxide particles and organic polymer where the weight percentof the inorganic oxide in the porous separator layer is greater thanabout 30% provide a heat resistant separator layer that retains itsdimensional stability at temperatures at and above 200° C.

Another aspect of the present invention pertains to methods of making alithium battery comprising the steps of (a) coating a porous separatorlayer on a substrate; (b) coating an electrode layer of a polaritydirectly on the separator layer; (c) coating one or more currentcollector layers directly on the electrode layer to make aseparator/electrode stack; (d) laminating two of the separator/electrodestacks together and delaminating the substrate from the separator layerto form a separator/electrode assembly having the one or more currentcollector layers interposed between the two electrode layers of theassembly; and (e) interleaving the assembly with an electrode comprisinga current collector layer interposed between two electrode layers ofopposite polarity to the electrode layer of step (b) to form a dryseparator/electrode cell. In one embodiment, the assembly and theelectrode are in a sheet configuration prior to the interleaving step.

Examples of suitable separator coatings for the present inventioninclude, but are not limited to, the separator coatings described inU.S. Pat. Nos. 6,153,337 and 6,306,545 to Carlson et al. and U.S. Pat.Nos. 6,488,721 and 6,497,780 to Carlson. These separator coatings may becoated from an aqueous mix or a solvent mix onto a variety ofsubstrates, such as, for example, silicone-treated plastic and papersubstrates, polyester film substrates, polyolefin-coated papers, metalsubstrates, porous polyolefin films, and porous non-woven polymer fibersubstrates. The advantages of coating the separator onto a substrate forthis invention include, but are not limited to, (a) that the otherlayers of the lithium battery may be coated or laminated overlying thisseparator coating layer and then subsequently the substrate may beremoved by delaminating to provide a dry stack of battery layers, (b)the coating process for the separator lends itself to making thinnerseparators than are typically available from an extrusion process forthe separator, and (c) the coated separator layer may be nanoporous withpore diameters of less than 0.1 microns that are too small to allow anypenetration of the particles of the electrode and other overlyingcoating layers into the separator layer. Even separator layers with porediameters up to 0.2 microns have been found to prevent the penetrationinto the separator layer of any particles of carbon black pigments asare typically used in lithium batteries.

As used herein, nanoporous layers are defined as layers where theaverage pore diameter is less than 100 nm, or, equivalently, less than0.1 microns. Since the particles in the electrode layer and in thecurrent collector layer, if the current collector layer comprises anyparticles, are larger than 0.1 microns in diameter and typically largerthan 0.5 microns in diameter, a coated separator layer with an averagepore diameter of less than 100 nm or 0.1 microns will prevent anypenetration into the separator layer by the particles of the electrodelayer and other overlying layers coated directly or indirectly on thenanoporous separator layer. In one embodiment of the lithium batteriesand of making lithium batteries of the present invention, the separatorlayer has a surface contour or profile that is the same before and afterthe coating of each of the two electrode layers on one of the separatorlayers, and the surface of each of the two electrode layers adjacent tothe separator layers has a contour that matches the contour of thesurface of each of the separator layers immediately adjacent to the twoelectrode layers. The non-penetration of the particles of the electrodecoatings into the separator layers contributes to this retention of thesurface contour of the separator layers. In one embodiment, each of thetwo electrode layers comprises electrode particles selected from thegroup consisting of electroactive particles and electrically conductiveparticles, and the electrode particles are not present in the separatorlayers. In one embodiment, the separator layer comprises separatorparticles, and the separator particles are not present in the twoelectrode layers. In one embodiment, the separator particles areselected from the group consisting of inorganic oxide particles,inorganic nitride particles, inorganic carbonate particles, inorganicsulfate particles, and organic polymer particles.

The electrode coating layer may be coated on the full surface of theseparator layer, or in lanes or strips on the separator layer, or inpatches or rectangle shapes on the separator layer, depending on therequirements of the end use and the specific approach to doing thecurrent collection from the layers of each electrode without having ashort circuit due to contacting any layers of the electrode and currentcollector of opposite polarity. Cathode coating layers typically arecoated from a pigment dispersion comprising an organic solvent, such asN-methyl pyrrolidone (NMP), and contain the electroactive or cathodeactive material in a pigment form, a conductive carbon pigment, and anorganic polymer. Anode coating layers typically are coated from apigment dispersion comprising an organic solvent or water, and containthe electroactive or anode active material in a pigment form, aconductive carbon pigment, and an organic polymer. The choice of whichelectrode layer, the cathode or the anode, is preferred for coating ontothe separator layer may be made based on the ease and quality of theelectrode coating and the ease and quality of doing subsequent coatingsteps, such as depositing the metal current collector layer. Forexample, it is generally easier to deposit an aluminum metal layer thanto deposit a copper or nickel metal layer, so coating the cathode layeron the separator layer to make the separator/electrode assembly istypically preferred. In this case, the anode may be made by the typicalmethod of coating the anode active layer on both sides of a copper ornickel substrate of about 10 microns in thickness.

In one embodiment of the lithium batteries and of making lithiumbatteries of this invention, the current collector layer of theseparator/electrode assembly comprises an electrically conductivematerial selected from the group consisting of electrically conductivemetals, electrically conductive carbons, and electrically conductivepolymers. The electrically conductive metals include, but are notlimited to, metal pigments, such as, for example, aluminum pigments,copper pigments, and nickel pigments. In one embodiment, the currentcollector layer of the assembly comprises two or more layers coateddirectly on one of the two electrode layers, and at least one of the twoor more layers comprises an electrically conductive material comprisingcarbon. In one embodiment, the thickness of the current collector layerof the assembly is less than 3 microns.

However, both the cathode and anode layers may be coated in aseparator/electrode assembly and those assemblies combined to form a dryseparator/electrode cell. In this case, the separator layer may bepresent on all of the electrode layers to give a “double separator”layer between the cathode and anode layers or, alternatively, may bepresent on only one electrode side of the separator/electrode assembly.

For the current collector layer, alternatively, a conductivenon-metallic layer, such as a carbon black coating, as known in the artof lithium batteries, may be coated before and/or after the depositionof the metal current collector layer in order to achieve improvedcurrent collection and battery efficiency, as well as added mechanicalstrength and flexibility. The metal current collector layer may be muchthinner than the typically 10 to 12 micron thick metal substrates usedin lithium batteries. For example, the metal current collector may havea thickness of less than 3 microns, and may be as thin as about 1micron, such as in the range of 0.5 to 1.5 microns thick. This allows ahigher proportion of electroactive material into the lithium battery,thereby enhancing the energy and power densities of the lithium battery.The metal current collector layer may be deposited by any of the metaldeposition methods known in the art, such as by vacuum deposition in thecase of aluminum layers.

FIG. 8 shows an example of a cross-section view (not to scale) of aseparator/electrode stack 50 after steps (a), (b), and (c).Separator/electrode stack 50 has a substrate 52, a separator layer 18,an electrode layer 16, and a current collector layer 14. FIG. 9 shows anexample of the multilayer structure formed by laminating two of theseparator/electrode stacks 50 together and has two substrates 52, twoseparator layers 18, two electrode layers 16, and a current collectorlayer 14. Delaminating the two substrates 52 in FIG. 9 from the adjacentseparator layers 18 results in the separator/electrode assembly, as, forexample, shown in FIG. 2.

The lamination and delamination steps may be done by any of thelamination and delamination methods known in the art, such as, forexample, by pressure lamination or heat lamination with pressure withthe materials of the surfaces to be laminated together being chosen tofacilitate the lamination.

The separator/electrode assembly and the electrode may be slit tonarrower widths and sheeted to desired shapes prior to interleaving themto make the dry separator/electrode cell with portions of the assemblyand of the electrode which are free of overlying and underlying layerswith electrodes of the opposite polarity and thus are in a configurationfor the current collection of multiple electrode layers of the samepolarity.

In one embodiment of the methods of preparing lithium batteries of thepresent invention, after step (e), a portion of the assembly is not incontact with the electrode and a portion of the electrode is not incontact with the assembly, and wherein a first device with electricallyconductive pins electrically connects two or more of the portions of theassembly and a second device with electrically conductive pinselectrically connects two or more of the portions of the electrode. Anexample of the resulting dry separator/electrode cell is shown in FIG.7. In one embodiment, there are further steps of (1) enclosing the dryseparator/electrode cell in a casing and (2) filling with electrolyteand sealing. Suitable casing materials and methods and electrolytefilling and sealing methods include those that are known in the art oflithium batteries. The casing helps to prevent any leakage ofelectrolyte and to provide additional mechanical protection. Theelectrolyte filling and sealing convert the dry separator/electrode cellinto a “wet” lithium battery ready for charge-discharge cycling andcustomer use.

In one embodiment of the methods of preparing lithium batteries of thisinvention, at least one of the one or more current collector layers ofstep (c) comprises a metal layer and the thickness of the metal layer isless than 3 microns, and preferably is about 1 micron, such as in therange of 0.5 to 1.5 microns thick. In one embodiment, the porousseparator comprises pores having an average pore diameter of less than0.2 microns, and preferably less than 0.1 microns. In one embodiment,the separator has a thickness of less than 9 microns, and is preferablyless than 6 microns.

The separator/electrode assembly and the electrode may be slit tonarrower widths and sheeted to desired shapes prior to interleaving themto make the dry battery cell with portions of the separator/electrodeassembly and of the electrode which are free of overlying and underlyinglayers with electrodes and current collectors of the opposite polarityand thus are in a configuration for the current collection of multipleelectrode and current collector layers of the same polarity. Also, theseparator/electrode assembly and the electrode may be slit to narrowerwidths and interleaved by offsetting them from each other similarly towhat is done in making cylindrical lithium batteries by winding togetherplastic separator, cathode, plastic separator, and anode strips ofdifferent widths and edge offsets from each other. Any of the methods ofedge connection known in the art of lithium batteries, such as, forexample, metal tabbing and vapor deposited metal edges, may also be usedfor the lithium batteries of this invention. Also, electricallyinsulating materials may be deposited on the edges of theseparator/electrode assembly or the electrode to provide additionalprotection against any short circuits with the electrode and currentcollector layers of opposite polarity.

The casing for the lithium batteries and methods of making lithiumbatteries of this invention may be designed to be useful in thepositioning and the alignment of the separator/electrode assembly andthe electrode in the interleaving step and also to be useful in thepositioning and placement of the device with the electrically conductivepins. For example, in one approach to making flat batteries, the bottomof the casing and four corner posts attached to the bottom couldposition and hold in place the interleaved separator/electrodeassemblies and electrodes at right angles to each other with a slightoverlap of each for about 4 to 10 mm on each edge positioned between twoof the four corner posts. Referring to FIG. 7, these four corner postscould be positioned at the four corners of the top down view to positionand hold in place the sheets during the interleaving step and prior tothe edge connection with the device with electrically conductive pins.To complete the battery fabrication, for example, the top of the casingcould be then attached to the four corner posts with openings on theedges of the top casing aligned with openings on the edges of the bottomcasing and positioned to accept the particular device with electricallyconductive pins. After doing the electrical connections on the edges,the remainder, if any, of the four sides of the casing could then beattached to the casing. These sides of the casing for flat batteries arelikely to be very short in height, such as less than 10 mm, compared tothe width of each side, such as about 100 to 200 mm. The casing may havea fill hole for the electrolyte as an opening on one of the sides,preferably on the top of the casing. After the filling with theelectrolyte, this fill opening is sealed to provide the “wet” batterythat is ready for formation cycling and testing before customer use.

The casing also provides the pathway for the electrical connections ofthe battery to the external circuits. This may be done in a variety ofways known in the art of lithium batteries and their casings. Forexample, the casing may be made of a metal, such as aluminum, as oneelectrode connection and of a metal pin that is electrically insulatedfrom the metal casing may be accessible on the outside of the casing asthe other electrode connection. Also, for example, the casing may beplastic and the devices with electrically conductive pins may beaccessible on the outside of the casing for each of the electrodes. Manyother variations of edge connection are available. For example, the edgeconnection for the separator/electrode assembly and the electrode forflat batteries could be done on only one edge, instead of on both edgesfor each. This approach could further simplify the fabrication of thebattery, while still providing effective edge connection. The length andwidth dimensions of the electrodes may be optimized to match with thepreferred edge connection and external electrical connection. Forexample, for the edge and external electrical connections on only oneside of each of the separator/electrode assembly and the electrode, thelength of that side might be much larger than the width distance to theside with no electrical connection.

Other electric current producing cells, such as batteries that are notlithium batteries and use a different battery chemistry and capacitors,may also be fabricated by methods similar to those describedhereinabove.

What is claimed is:
 1. A method of making a lithium battery, the methodcomprising the steps of: (a) coating a porous separator layer on asubstrate; (b) coating or laminating a first electrode layer of apolarity overlying said separator layer; (c) coating or laminating asecond electrode layer of the same polarity overlying said separatorlayer; (d) coating, laminating, or depositing one or more currentcollector layers overlying said first electrode layer to make aseparator/electrode stack; (e) laminating said second electrode layer tosaid one or more current collector layers on the side opposite to saidfirst electrode layer and delaminating said substrate from saidseparator layer to form a separator/electrode assembly having said oneor more current collector layers interposed between said first andsecond electrode layers; and (f) interleaving said assembly with anelectrode comprising a current collector layer interposed between twoelectrode layers of opposite polarity to said first and second electrodelayers of steps (b) and (c) to form a dry cell.
 2. The method of claim1, wherein said assembly and said electrode are in a sheet configurationprior to said interleaving step.
 3. The method of claim 1, wherein thereare further steps of (1) enclosing said dry cell in a casing and (2)filling with electrolyte and sealing.
 4. The method of claim 1, whereinsaid one or more current collector layers comprises a metal layer. 5.The method of claim 4, wherein an edge connection of said one or morecurrent collector layers comprises metal tabbing.
 6. The method of claim4, wherein the thickness of said metal layer is less than 3 microns. 7.The method of claim 1, wherein said first and second electrode layers ofsaid assembly are anode layers.
 8. The method of claim 7, wherein saidone or more current collector layers comprises a metal layer selectedfrom the group consisting of a copper layer and a nickel layer.
 9. Themethod of claim 1, wherein said first and second electrode layers ofsaid assembly are cathode layers.
 10. The method of claim 9, whereinsaid one or more current collector layers comprises an aluminum layer.11. The method of claim 1, wherein said first and second electrodelayers are coated directly on said separator layer from a pigmentdispersion comprising an organic solvent or water.
 12. The method ofclaim 1, wherein said separator layer comprises inorganic oxideparticles in an amount greater than 30% by weight.
 13. The method ofclaim 1, wherein there are no pores larger than 0.2 microns in diameterin said porous separator layer.
 14. The method of claim 1, wherein saidseparator layer comprises a xerogel layer.
 15. The method of claim 1,wherein said separator layer has a thickness of less than 9 microns. 16.The method of claim 1, wherein said separator layer comprises aluminumboehmite.
 17. The method of claim 1, wherein said separator layer is aheat resistant separator layer with dimensional stability at 200° C. 18.The method of claim 1, wherein said separator layer comprises poreshaving an average pore diameter of less than 0.1 microns.
 19. A methodof making a lithium battery, the method comprising the steps of: (a)coating a porous separator layer on a substrate, the porous separatorlayer comprising inorganic oxide particles in an amount greater than 30%by weight, having no pores larger than 0.2 microns, and comprising axerogel layer; (b) coating an electrode layer of one polarity from apigment dispersion comprising an organic solvent or water directly onsaid porous separator layer; and (c) coating, laminating, or depositingone or more current collector layers directly on said electrode layer tomake a separator/electrode stack.
 20. The method of claim 19, whereinsaid method further comprises the steps of: (d) laminating two of saidstacks together and delaminating said substrate from said separatorlayer to form a separator/electrode assembly having said one or morecurrent collector layers interposed between the two electrode layers ofsaid two stacks; and (e) interleaving said assembly with an electrodecomprising a current collector layer interposed between two electrodelayers of opposite polarity to said electrode layer of step (b) to forma dry cell.
 21. The method of claim 20, wherein there are further stepsof (1) enclosing said dry separator/electrode cell in a casing and (2)filling with electrolyte and sealing.